Suppose I have the following sudoku: problem <- matrix(c( 5, 3, 0, 0, 7, 0, 0, 0, 0, 6, 0, 0, 1, 9, 5, 0, 0, 0, 0, 9, 8, 0, 0, 0, 0, 6, 0, 8, 0, 0, 0, 6, 0, 0, 0, 3, 4, 0, 0, 8, 0, 3, 0, 0,...

What is the difference between backtracking and recursion? How is this program working? void generate_all(int n) { if(n<1) printf("%s\n", ar); else{ ar[n-1]='0'; //fix (n)th bit as ...

I'm encountering an issue where preg_replace() with a complicated regular expression causes an error (PREG_BACKTRACK_LIMIT_ERROR) due to pcre.backtrack_limit being too low, which is set to 1,000,00...

Find twelve 32-bit numbers such that each pair of them differs by bits in at least 17 positions. I'm struggling to find and optimal algorithm for this problem. More general question is: Find 'n' 32...

I have read in Wikipedia and have also Googled it, but I cannot figure out what "Backtracking Algorithm" means. I saw this solution from "Cracking the Code Interviews" and wonder why is this a ...

A multi-set is a set in which all the elements may not be unique.How to enumerate all the possible permutations among the set elements?

Given a string S of length N, return a string that is the result of replacing each '?' in the string S with an 'a' or a 'b' character and does not contain three identical consecutive letters (in ot...

The problem I am talking about is the one below : Consider a rat placed at (0, 0) in a square matrix m[ ][ ] of order n and has to reach the destination at (n-1, n-1). The task is to find a sorted...

I'm trying to write a code that split a spaceless string into meaningful words but when I give sentence like "arealways" it returns ['a', 'real', 'ways'] and what I want is ['are', 'alway...

Now I'm working with the recursive backtracking,my assignment is to find the longest path in the maze,the mass is presented as the field covered with the coordinates,and the coordinates of the wall...

I found from various online coding forums, there is a technique called "AC", which looks like "Dynamic Programming" or "Back tracking", but not sure what it is how to ...

def paren(n): lst = ['(' for x in range(n)] current_string = ''.join(lst) solutions = list() for i in range(len(current_string)+1): close(current_string, n, i, solutions) return solutions de...

So I've been trying to solve this assignment whole day, just can't get it. The following function accepts 2 strings, the 2nd (not 1st) possibly containing *'s (asterisks). An * is a replacement fo...

Lets say that you are given n sorted arrays of numbers and you need to pick one number from each array such that the minimum distance between the n chosen elements is maximized. Example: arrays: [0...

I'm trying to understand how the Select monad works. Apparently, it is a cousin of Cont and it can be used for backtracking search. I have this list-based solution to the n-queens problem: -- All...

Algorithm NQueens ( k, n) //Prints all Solution to the n-queens problem { for i := 1 to n do { if Place (k, i) then { x[k] := i; if ( k = n) then write ( x [1 : n] else NQueens ( k+1, n); }...

I code the Knight's tour algorithm in c++ using Backtracking method. But it seems too slow or stuck in infinite loop for n > 7 (bigger than 7 by 7 chessboard). The question is: What is the Time c...

Consider the usage of these different parser combinators. import Control.Applicative.Combinators import Text.Regex.Applicative main :: IO () main = do let parser1 = sym '"' *> manyTill a...

I am programming a Sudoku solver in Java for a 9x9 grid. I have methods for: printing the grid initializing the board with given values testing for conflicts (if same number is in same line or 3...

The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, We get the following sequence (ie, for n = 3 ) : "123" "132" "213" "231"...

I have a crossword puzzle and a list of words which can be used to solve it (words can be placed multiple times or not even once). There is always a solution for the given crossword and word ...

I'm trying to understand the semicolon functionality. I have this code: del(X,[X|Rest],Rest). del(X,[Y|Tail],[Y|Rest]) :- del(X,Tail,Rest). permutation([],[]). permutation(L,[X|P]) :- del(X,L,L...

In backtracking we use both bfs and dfs. Even in branch and bound we use both bfs and dfs in additional to least cost search. so when do we use backtracking and when do we use branch and bound Do...

We have a REST API for querying records in a MongoDB. Very simple, something along the following: GET /api/items?q=foo During development, it was convenient to allow regular expressions as the q...

"Programming Challenges (The Programming Contest Training Manual)" is probably one of the nicest exercises book on algorithms. I've resolved the first 11 exercises, but now I am stuck with "Crypt K...